for j in startTime.value to endTime.value by div1 do --key vertices of first spline ( sliderTime = j in coordsys tread1 (zipStep[count1] = zip1.pos) --cache position of box (using the spline's coordinate system), over time in coordsys world (dumStep[count1] = zip1.pos)

if help1.checked == true then --if the user wants helpers to be created, create them! ( at time (j-(div1*2)) (ht1[count1].pos = (in coordsys world (getknotpoint tread1 1 count1))) addNewKey ht1[count1].pos.controller (j-(div1*2)) with animate on ( at time j (ht1[count1].pos = dumStep[count1]) ) ) count1 += 1 --increase counter (this counter is used to cycle through vertices, as well as to cycle through the zipper's position cache) updateshape tread1 if count1 > (numknots tread1 1) then exit --exit when we've cycled through all available vertices )

for j in startTime.value to endTime.value by div2 do --key vertices of second spline (same as above) ( sliderTime = j in coordsys tread2 (zipStep2[count2] = zip1.pos) in coordsys world (dumStep2[count2] = zip1.pos)